Patent Document 1, shown below as a prior art document related to this type of a single glass panel for a fire door or a double glazed glass panel for a fire door, proposes, as a glass panel for a fire door, a glass panel obtained by forming a heat reflecting coating (Low-E coating) on at least one surface of a fireproof glass sheet such as a low expansion glass sheet, wired glass sheet and transparent crystallized glass sheet, and a double glazed glass panel obtained by combining this fireproof glass sheet and a standard glass sheet, which is not a fireproof glass sheet. Patent Document 1 states that the heat reflecting coating is used only for the purpose of restricting the conduction of radiant heat given off by a fire and preventing the temperature in rooms where a fire has not broken out from increasing while maintaining the transparency of the glass sheet.
Substantially similarly to Patent Document 1, Patent Document 2, shown below as another prior art document, also proposes, as a glass panel for a fire door, a single fireproof glass sheet in which a heat reflecting coating and an antioxidation coating are formed on at least one surface thereof, and a double glazed glass panel obtained by combining this fireproof glass sheet and another fireproof glass sheet. This document also states that the heat reflecting coating is used only for preventing a fire from spreading to adjacent rooms due to a heat insulating effect while maintaining the transparency of the glass sheet even when the fire breaks out.